The application described herein relates generally to gas turbine engines components, and more specifically to methods and assemblies for outlet guide vanes and driveshaft vessels.
At least some known gas turbine engine assemblies include a fan assembly that is mounted upstream from a core gas turbine engine. During operation, a portion of the airflow discharged from the fan assembly is channeled downstream to the core gas turbine engine wherein the airflow is further compressed. The compressed airflow is then channeled into a combustor, mixed with fuel, and ignited to generate hot combustion gases. The combustion gases are then channeled to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight. The other portion of the airflow discharged from the fan assembly exits the engine through a fan stream nozzle.
To facilitate channeling the airflow from the fan assembly to the fan stream exhaust, at least some known gas turbine engine assemblies include an outlet guide vane assembly that is used to remove swirl in the airflow upstream of the fan exhaust. Such an outlet guide vane assembly is configured to turn the airflow discharged from the fan assembly to a substantially axial direction prior to the fan flow being exhausted from the bypass duct. In addition to straightening the fan airflow, the outlet guide vane assembly also provides structural stiffness to the fan frame. More specifically, outlet guide vane assemblies generally include a plurality of outlet guide vanes that are coupled to the fan frame.
In addition to outlet guide vanes, many fan frame assemblies include one or more (frequently two, diametrically opposed) dividing structures, often called bifurcations, which divide the annular space defined by the bypass duct into two semi-annular spaces. These dividing structures are typically hollow duct-like structures through which various mechanical, electrical, pneumatic, hydraulic, or other connections (including structural supports) can pass without causing disruption to the airflow through the bypass duct. The bifurcations fair or guide the flow in aerodynamic fashion around these structures, and may be integrated or blended into the profile of an upstream guide vane to reduce the number of individual airflow disruptions.
Gas turbine engines also typically include an accessory gear box normally mounted in its own casing at the exterior of the gas turbine engine casing. The gear box is mechanically interconnected to the primary central driveshaft of the engine through a radial driveshaft. During normal operation, the radial driveshaft transfers power from the engine core to the accessory gearbox, and, during engine startup, the radial driveshaft also transfers power from the starter located in the accessory gearbox to the engine core.
Since the radial driveshaft runs through the fan stream of the engine, the driveshaft requires a protective cover to contain surrounding air and oil required for standard driveshaft operation. Hollow struts are typically used to contain the radial driveshaft along with other services necessary for operation, such as oil or air lines, that run from the core of the engine to the gearbox. These struts that cover the radial driveshaft run through the fan stream and cause significant drag, which has a negative effect on specific fuel consumption and efficiency. Accordingly, there remains a need for a driveshaft vessel assembly covering the radial driveshaft while minimizing drag by eliminating the presence of a strut.